Don't put private members in dart:html interfaces.

client/html/generated/html/dartium/Element.dart

Index: client/html/generated/html/dartium/Element.dart
diff --git a/client/html/generated/html/dartium/Element.dart b/client/html/generated/html/dartium/Element.dart
index 4748aad82a10202304007bc0a703861edaae0ff3..d78609b9b83c8151612540655949fff4a25744d9 100644
--- a/client/html/generated/html/dartium/Element.dart
+++ b/client/html/generated/html/dartium/Element.dart
@@ -533,9 +533,10 @@ class _ElementImpl extends _NodeImpl implements Element {
   }
 
   Future<CSSStyleDeclaration> getComputedStyle(String pseudoElement) {
-    return _createMeasurementFuture(() =>
-            window._getComputedStyle(this, pseudoElement),
-        new Completer<CSSStyleDeclaration>());
+    return _createMeasurementFuture(() {
+      final _WindowImpl win = window;
+      return win._getComputedStyle(this, pseudoElement);
+    }, new Completer<CSSStyleDeclaration>());
   }
   _ElementImpl._wrap(ptr) : super._wrap(ptr);